Operation of the SPS

A number of operation modes of the SPS have been investigated, where the number of protons on target per year has served as an important parameter in defining these schemes [5]. The proposed SPS cycle configuration is presented below, optimised for the NGS and for the users of the SPS requiring a flat top slow extraction (SE) spill structure.

The following assumptions have been used as input into the definition of a future SPS super-cycle :

• The current LEP cycles (2.4s total duration) will no longer be required.
• The average SPS power dissipation over the duration of the super-cycle should respect the limit of 33MW.
• The SPS should be able to provide a SE at 450GeV/c with a duty cycle around the present 16%.
• The combination of a FE with a SE in one cycle seems to be very difficult, and no solution exists at present. It is instead possible to combine FS with SE in one cycle.

Figure2 shows the proposed SPS super-cycle which could be used to provide protons for the shared mode of FE and SE physics. The super-cycle consists of separate cycles for the SE physics and for the FE neutrino programme, thus decoupling the parameters (e.g. incident proton momenta) requested by the two communities.

  
Figure: The proposed SPS super-cycle. The parameter is the incident proton momentum for the neutrino cycles and has been studied for various values between 350 and 450 GeV/c. For one obtains  sec.

As a working hypothesis, the maximum number of protons per SPS cycle is assumed to be 4.5 10 , a value which has been safely reached and even surpassed in 1997. Given the planned improvements in the SPS and PS complex for the LHC [6, 7], it is likely that the maximum achievable intensity will increase further so that 4.5 10 protons could be safely assumed for normal SPS operation.

A graphite target is expected to sustain the thermal shock induced by the impinging protons [5]. For the two fast-extraction scheme proposed for the NGS, the graphite target limit at 400 GeV/c is protons per extraction, thus exploiting the full SPS intensity.

Therefore, the number of protons on target per year, defined as a 200-day run with a global machine efficiency of , for the proposed cycle at 400 GeV/c is calculated to be protons.

Finally, for comparison, Figure3 shows the configuration of a dedicated neutrino cycle. At 400 GeV/c, the number of protons on to the neutrino target per year is estimated to be Obviously, the gains for the NGS are substantial, but at the expense of the SE programme. However, given that such a neutrino mode of operation is relatively inexpensive in terms of electrical power, due to the absence of an extended flat-top, the neutrino beam could operate for periods extending beyond the normal SPS proton fixed target operation.

  
Figure 3: The dedicated neutrino operation mode of the SPS.